This invention relates to an apparatus which is associated with a packaging machine and which serves for the making of packaging bags from converging separate sealable sheets directed by means of sheet guides to a first sealing station where longitudinal seams are provided and to a second sealing station where the sealing sheets are sealed together by transverse seams.
U.S. Pat. No. 4,291,520 discloses an apparatus wherein a wrapper sheet drawn from a supply reel is shaped about a hollow mandrel by a shaping shoulder and subsequently a longitudinal seam and transverse seams are formed. The bags are charged with the goods by means of the hollow mandrel. The filled bags which are closed with three seams are subsequently severed from the sheets. A further example of a packaging machine of this type is described in Swiss Pat. No. 416,434 or British Pat. No. 1,271,214.
British Pat. No. 1,271,214 discloses a plurality (for example, four) hollow mandrels arranged side by side. The two wrapper sheets are sealed by means of sealing rollers in the zone of the hollow mandrels along five paths so that four side-by-side arranged bags are formed. Underneath the discharge end of the hollow mandrels a pair of sealing shoes are provided for forming a transverse seam. Cutting means for severing the bags from the sheets are incorporated in the sealing shoes. By means of a rotary roller provided with suction cups the bag rows, each contaning four bags, are deposited into conveying compartments of a conveyor apparatus.
According to Swiss Pat. No. 416,434, a wrapper sheet is withdrawn from a single supply reel and then divided in the middle into two wrapper sheets which are directly advanced to a shaping guide by a deflecting mechanism. Thereafter, rollers provide longitudinal and transverse sealing ribs on the bag. Subsequent to sealing the bags on all sides, they are severed first longitudinally and then in a transverse direction.
No guide arrangements for the wrapper sheets prior to the sealing step are provided in either of the above-outlined conventional structures; rather, both wrapper sheets are directly shaped about the hollow mandrel and then sealed. Relatively rigid films cannot be processed in this manner because during the filling step and during the provision of the longitudinal seam a tension in the transverse direction is generated so that the sealing seam cannot be made without stresses. Such seams result in defective seals. This problem could be avoided if it were possible to cut the wrapper sheets into strips before their shaping. In both of the above-described conventional arrangements, the cutting stations are situated downstream of the sealing station as viewed in the direction of wrapper sheet advance. It is, however, not feasible to arrange a longitudinal cutter upstream of the shaping and sealing stations in the described structures, because a sufficient lateral guide is not present and, as a result, the wrapper strips would run off laterally.